They will respond back, they are responding to cases base on how case are submitted. With numbers of backlog they have. Every case have different issue and it maybe background check, marriage, fraud etc.
Tell your petitioner to try either of this number below. Department Of State. +1 (202) 647-4000, +1 (202) 485-7600, +1 (800) 877-8339 or US consulate Lagos Nigeria +234 1 440 6218, +234 1 227 8955, +234 1 460 3400, +234 1 460 3600.